A standard sealing machine has a pair of sealing tools each formed with an array normally uniformly distributed bumps. The tools are heated and pressed together to opposite sides of a pair of thermoplastic foils to laminate them together, with each of the bumps pressing a predetermined depth, which is substantially less than the foil thickness, into the respective face of the foils.
The problem with designing such tools is that it is normally a hit and miss job determining the spacing between the bumps. This spacing varies with their area, the pressures used and so on. Thus it is standard simply to make up a tool, try it out, then remachine or replace it as necessary until the desired pattern and sealing is obtained. The result is often a tradeoff between product quality, that is how good the seal is, and the work in designing the sealing tools.